From 36dccc845b1821fccacc93fe1ede85a1b5f0422d Mon Sep 17 00:00:00 2001
From: tzugen <tzugen@riseup.net>
Date: Sun, 20 Jun 2021 08:24:14 +0200
Subject: [PATCH] Use ListAdapter class to calculate Diff off the main thread

---
 .../moire/ultrasonic/domain/GenericEntry.kt   | 14 ++++++-
 .../ultrasonic/fragment/GenericRowAdapter.kt  | 41 ++++++++-----------
 2 files changed, 29 insertions(+), 26 deletions(-)

diff --git a/core/domain/src/main/kotlin/org/moire/ultrasonic/domain/GenericEntry.kt b/core/domain/src/main/kotlin/org/moire/ultrasonic/domain/GenericEntry.kt
index 194408e6..37bd863f 100644
--- a/core/domain/src/main/kotlin/org/moire/ultrasonic/domain/GenericEntry.kt
+++ b/core/domain/src/main/kotlin/org/moire/ultrasonic/domain/GenericEntry.kt
@@ -1,7 +1,19 @@
 package org.moire.ultrasonic.domain
 
 abstract class GenericEntry {
-    // TODO Should be non-null!
+    // TODO: Should be non-null!
     abstract val id: String?
     open val name: String? = null
+
+    // These are just a formality and will never be called,
+    // because Kotlin data classes will have autogenerated equals() and hashCode() functions
+    override operator fun equals(other: Any?): Boolean {
+        return this === other
+    }
+
+    override fun hashCode(): Int {
+        var result = id?.hashCode() ?: 0
+        result = 31 * result + (name?.hashCode() ?: 0)
+        return result
+    }
 }
diff --git a/ultrasonic/src/main/kotlin/org/moire/ultrasonic/fragment/GenericRowAdapter.kt b/ultrasonic/src/main/kotlin/org/moire/ultrasonic/fragment/GenericRowAdapter.kt
index 9e52e4e8..b825fcac 100644
--- a/ultrasonic/src/main/kotlin/org/moire/ultrasonic/fragment/GenericRowAdapter.kt
+++ b/ultrasonic/src/main/kotlin/org/moire/ultrasonic/fragment/GenericRowAdapter.kt
@@ -17,6 +17,7 @@ import android.widget.PopupMenu
 import android.widget.RelativeLayout
 import android.widget.TextView
 import androidx.recyclerview.widget.DiffUtil
+import androidx.recyclerview.widget.ListAdapter
 import androidx.recyclerview.widget.RecyclerView
 import org.moire.ultrasonic.R
 import org.moire.ultrasonic.data.ActiveServerProvider
@@ -31,7 +32,8 @@ abstract class GenericRowAdapter<T : GenericEntry>(
     val onItemClick: (T) -> Unit,
     val onContextMenuClick: (MenuItem, T) -> Boolean,
     private val onMusicFolderUpdate: (String?) -> Unit
-) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
+) : ListAdapter<T, RecyclerView.ViewHolder>(GenericDiffCallback()) {
+
     open var itemList: List<T> = listOf()
     protected abstract val layout: Int
     protected abstract val contextMenuLayout: Int
@@ -46,10 +48,8 @@ abstract class GenericRowAdapter<T : GenericEntry>(
      * using DiffUtil to efficiently calculate the minimum required changes..
      */
     open fun setData(data: List<T>) {
-        val callback = DiffUtilCallback(itemList, data)
-        val result = DiffUtil.calculateDiff(callback)
+        submitList(data)
         itemList = data
-        result.dispatchUpdatesTo(this)
     }
 
     /**
@@ -138,29 +138,20 @@ abstract class GenericRowAdapter<T : GenericEntry>(
         var coverArtId: String? = null
     }
 
-    /**
-     * Calculates the differences between data sets
-     */
-    open class DiffUtilCallback<T : GenericEntry>(
-        private val oldList: List<T>,
-        private val newList: List<T>
-    ) : DiffUtil.Callback() {
-        override fun getOldListSize(): Int {
-            return oldList.size
-        }
-        override fun getNewListSize(): Int {
-            return newList.size
-        }
-        override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
-            return oldList[oldItemPosition].id == newList[newItemPosition].id
-        }
-        override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
-            return oldList[oldItemPosition] == newList[newItemPosition]
-        }
-    }
-
     companion object {
         internal const val TYPE_HEADER = 0
         internal const val TYPE_ITEM = 1
+
+        /**
+         * Calculates the differences between data sets
+         */
+        class GenericDiffCallback<T : GenericEntry> : DiffUtil.ItemCallback<T>() {
+            override fun areContentsTheSame(oldItem: T, newItem: T): Boolean {
+                return oldItem == newItem
+            }
+            override fun areItemsTheSame(oldItem: T, newItem: T): Boolean {
+                return oldItem.id == newItem.id
+            }
+        }
     }
 }